1. Field of the Application
The procedure and device shown and described herein are for continuous sterilization of solid urban waste, livestock waste, agricultural waste and products, and food products. The waste or products are placed in a pressure tank, called the reactor, and submitted to certain elevated temperatures and pressures for a variable time depending on the material to be sterilized, such that the product is completely sterilized when taken out. Waste treated in this way is transformed and may be used subsequently.
2. Background
Closed-recipient stream-injection sterilization systems to sterilize medical waste, food products, woods, etc., are well-known. These systems are comprised of several phases: temperature and pressure increase, temperature maintenance for sterilization, cool-down, and decompression (removal of all internal steam).
Some of these systems are used to sterilize solid urban waste and home garbage. The organic material involved is transformed by the process and may be used again, once it is partially dried, to generate energy and even to manufacture products.
Generally cylindrical pressure tanks are used in this type of processes, and the waste in the tank is submitted to a certain temperature and pressure. Movement within the tank facilitates the separation of the materials and the extraction of the water they contain. For this reason, the processes already in use consist of several phases in the pressure tank. As we have said above:
Temperature increase phase
Temperature maintenance for sterilization phase
Cool-down phase
Decompression phase (elimination of all internal steam)
As part of the state of the art, the following documents are exemplary: U.S. Pat. No. 5,427,650; WO 03026101; WO 2007/079968; WO 2008/065002; WO 2008/010854; U.S. Pat. No. 7,303,160; WO 03/025101; EP 0 870 433; U.S. Pat. No. 5,091,158; GB 2,452,289; GB 2,456,074.
System of a company called Ambiensys S.L., as described in patent applications PCT/EP2006/012556, and PCT/EP2007/062353 process wastes in semi-continuous way by introducing limited quantities of waste by batches at various times during the process. This system also relies on gravity to remove processed material from the system.
The systems of the prior art have inherent problems arising from the periodic introduction of large quantities of waste to be sterilized in the pressure tank and/or the inefficiency in which the waste is handled. In batch processing, significant energy is wasted, since for each batch the tank must be pressurized, steam injected, temperature and pressure maintained for the time necessary for sterilization, the tank depressurized, and the batch of waste removed. Each of these phases inherently requires major energy consumption, besides prolonging the time necessary for processing each batch.
Apart from this, the processes used are rather complex to inject steam and to extract liquids while maintaining the pressure, temperature, and rotary movement within the pressure tank.